(a) Field of the Invention
This invention relates to car clocks and more particularly to improvements in an electronic digital type car clock utilizing a battery of an automobile as a current source and provided with a time counting part and a time indicating part.
(b) Description of the Prior Art
In the arrangement of a conventional car clock, as shown in FIG. 1, the voltage of a battery 1 of an automobile is normally fed through a constant voltage circuit 2 to a time counting part consisting of an oscillating circuit 3 as a time reference signal source, a counting circuit 4 and a decoder 5 and the voltage is fed to a time indicating part 6 through a resistor 8 by a switch 7 to be on as interlocked with the operation, for example, only when the engine key is rotated to the ON-position so that the power consumption may be reduced by avoiding the continuous lighting of the time indicating part 6 high in the power consumption.
However, in such conventional circuit, the resistor 8 is used to control the voltage when a fluorescent discharge tube is used for the indicating element of the time indicating part 6 and to control the current when a luminous diode is used for the indicating element and as a result, a comparatively large electric power will be wasted by this resistor 8.